Add `resident` field cache type, closes #602.

modules/elasticsearch/src/main/java/org/elasticsearch/index/cache/field/data/resident/ResidentFieldDataCache.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.cache.field.data.resident;
+
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.Index;
+import org.elasticsearch.index.cache.field.data.support.AbstractConcurrentMapFieldDataCache;
+import org.elasticsearch.index.field.data.FieldData;
+import org.elasticsearch.index.settings.IndexSettings;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * @author kimchy (shay.banon)
+ */
+public class ResidentFieldDataCache extends AbstractConcurrentMapFieldDataCache {
+
+    @Inject public ResidentFieldDataCache(Index index, @IndexSettings Settings indexSettings) {
+        super(index, indexSettings);
+    }
+
+    @Override protected ConcurrentMap<String, FieldData> buildFieldDataMap() {
+        return new ConcurrentHashMap<String, FieldData>();
+    }
+
+    @Override public String type() {
+        return "resident";
+    }
+}